1. Field of Invention
The present invention relates generally to phase locked loops. More particularly, the present invention relates to a device and method for measuring jitters in phase locked loops.
2. Description of Related Art
Due to rapid progress in electronic technologies, all kinds of electronic devices have been developed to ease our daily life. As electronic devices continue to improve, people rely upon the operational stability of the devices heavily. Phase locked loop (PLL) is one of the most commonly used electronic devices in the technologies, a PLL contains essentially a phase detector, amplifier, and voltage controlled oscillator (VCO). A few of its applications are tone decoding, demodulation of AM and FM signals, frequency multiplications, frequency synthesis, pulse synchronization of signals from noisy sources, and regeneration of “clean” signals. The jittering content of a phase locked loop is one principle factor that affects the phase locked loop performance as well as circuit stability. Hence, the jitter within a phase lock loop signal must be carefully monitored.
In the past, signal jitters are often monitored visually through an oscilloscope or other instruments. In a visual inspection, minor differences may escape our visual detection and the observed jitters are difficult to measure. Moreover, apart from the need of operating a complicated instrument for jitter measurements, the measured results are not available to be used by other circuits within the same device, unlike a built-in device.